Theoretical And Experimental Research On Metal Photo-Thermal Micro Actuator

MEMS (Micro-Electro-Mechanical-System) is always heading towards the trend of being smaller and multi-functional, at the same time micro actuators enjoy a great development, emerges in large numbers of various actuate techniques such as electrostatic, electromagnetic, piezoelectricity, electro thermal, photo thermal techniques. Among them, photo thermal technique has the advantages of simple structure, easy control, large output, remote control, small size and easy integrated property. Usually photo resister, HDPE, PMMA and such polymers are used to fabricate photo thermal actuators. These polymer actuators suffer from the limitations of structure strength, heat tolerance, reliability, slow dynamic response. Therefor we proposed a metal photo thermal actuator, which has a great improvement over the above shortcomings. Several metal photo thermal actuators are fabricated with LIGA technique, and series experiments are carried out.Systematic researches on photo thermal expansion mechanism and photo thermal actuate technique are carried out, and both steady and transient models of a photo thermal expansion arm’s actuation driven by a laser beam are established. First we discuss the physic phenomenon involved in the photo thermal process, like laser absorbing, thermal conduction, convection, radiation, and thermal expansion. Then steady and transient models are established, and take the example of a micro expansion arm to calculate the temperature distribution and deformation, with the driving of continuous and pulse laser, separately.Several kinds of metal photo thermal actuators are design and fabricated. On the base of theoretical models, triangle shape micro actuator, ratchet pawl micro motor and worm scrawl micro actuator are proposed. These actuators are fabricated in LIGA beam line of BSRF, with LIGA technique.Experimental system for photo thermal driving and microscopic observation is set up and optimized. It is composed by the driving module and microscopic observation module. The driving module contains a laser source and modulation optical path, which can tuning the laser wave form and focus it on the driving position accurately, to drive photo thermal actuators. The microscopic observation module contains the functions of microscopic monitoring and actuation analysis. The software based on image matching algorithm can describe the actuation curve very well.Research on actuation property of the triangle shape photo thermal micro actuator is carried out. First, geometry structure and actuation principle of the actuator are demonstrated. Then the steady and transient temperature distribution and deformation are simulated by Finite Element Analysis tools, with driving of continuous and pulse laser, especially the dynamic response property when actuators are driven by lasers of different frequencies. Actuators made from Nickel are investigated in the experiments, and the results show great agreement with simulations. At last not the least, the effects of several important material parameters on the actuation behavior are investigated, with Finite Element Analysis method.A ratchet pawl photo thermal micro actuator and a worm scrawl photo thermal actuator are demonstrated. Geometry structure and working mechanism of the photo thermal micro motor are demonstrated, which can turn linear reciprocating motion into rotation. Samples are fabricated with LIGA tech, and driving experiments are carried out. The results verified the feasibility to transform light energy directly into rotate energy with a mechanic device. A worm scrawl photo thermal actuator is proposed, which is expected to scrawl forward with driving of a pulse laser.